Contact lenses are widely used for correcting many different types of vision deficiencies. These include defects such as near-sightedness and far-sightedness (myopia and hypermetropia, respectively), astigmatic vision errors, and defects in near range vision usually associated with aging (presbyopia).
Current opinion holds that presbyopia occurs as a person ages when the lens of eye begins to crystallize and lose its elasticity, eventually resulting in the eye losing its accommodation—the ability to focus on nearby objects.
Some presbyopic persons have both near vision and far vision defects, requiring bifocal lenses to properly correct their vision. Many people prefer wearing contact lenses to correct their vision rather than bifocal or progressive spectacles. However, creating a bifocal or simultaneous vision lens for presbyopes entails finding the optimal visual “compromise” between near and far vision. The registration or location of the contact lens on the cornea, does not allow selection of the ADD zone as a function of gaze.
Testing refractive errors of the eye involves several tests, some of which are subjective, and others that are objective in nature. Objective refraction tests include the use of retinoscopy, phoropter systems, wavefront sensors and autorefractors. A phoropter can be manipulated by a control unit so that an operator's movement can be minimized during the testing procedure (see U.S. Pat. No. 4,861,156), and is expressly incorporated by reference as if fully set forth herein.
Wavefront sensors may also be used to detect refractive errors in the eye, such as for example, a Shack-Hartmann wavefront sensor. Measurements of the wavefront aberrations of the eye to a high degree of precision using an improved Hartmann-Shack wavefront sensor are described in U.S. Pat. No. 5,777,719, which is expressly incorporated by reference as if fully set forth herein. The wavefront sensor illuminates the retina with a narrow beam of light and then determines the refractive error of the eye, at all points in the pupil, by analysis of the outgoing wavefront scattered by the retina. Typically, this wavefront is fit to a basis set such as the Zernike index.
Objective refraction tests often to not correlate with subjective sphero-cylindrical correction or presbyopic correction. Furthermore, objective refractions are typically determined only at the distance conjugate in a monocular fashion. Differences in an eye's aberration, the individual's neural processing and visual requirements may limit the effectiveness of objective tests as vision is subjective. Subjective eye tests are more interactive than objective tests and may better encompass the entire visual system, The present invention seeks to correct the inadequacies of the prior art such as that included in adaptive optic phoropter systems by the inclusion of high spatial frequency adaptive optic technology, an optometer to vary the vergence of the visual stimulus and a binocular configuration to incorporate modified monovision into the lens designs. In the preferred embodiment of the present invention, the system has the ability to provide high spatial frequency aberration patterns, through focus, in a binocular fashion. As such, the system will simultaneously demonstrate the expected though focus vision to a subject and provide the information to calculate the customized lens designs